The present invention relates generally to medical devices and methods. More specifically, the present invention relates to ultrasound catheter devices, methods for making the devices, and methods for using the devices to disrupt blood vessel occlusions.
Catheters employing various types of ultrasound transmitting members have been successfully used to ablate or otherwise disrupt obstructions in blood vessels. Specifically, ablation of atherosclerotic plaque or thromboembolic obstructions from peripheral blood vessels such as the femoral arteries has been particularly successful. To disrupt occlusions of small blood vessels, such as coronary arteries or peripheral vessels, ultrasound catheters typically have configurations—size, flexibility, shape and the like—which allow for their advancement through the tortuous vasculature of the aortic arch, coronary tree, peripheral vasculature or other similarly narrow vessels.
Typically, an ultrasound catheter transmits energy from an ultrasound transducer through a transducer horn and then a transmission member, such as a wire, to a distal tip or distal head. Ultrasound energy propagates through the transmission member as a sinusoidal wave to cause the distal head to vibrate. Such vibrational energy is typically utilized to ablate or otherwise disrupt vascular obstructions. Various ultrasonic catheter devices have been developed for use in ablating or otherwise removing obstructive material from blood vessels. For example, U.S. Pat. Nos. 5,267,954 and 5,380,274, issued to the inventor of the present invention and hereby incorporated by reference, describe ultrasound catheter devices for removing occlusions. While many ultrasound catheters have been developed, however, improvements are still being pursued.
To effectively reach various sites for treatment of intravascular occlusions, ultrasound catheters often have lengths of about 150 cm or longer. To reach some sites, such as arterial side-branches, it is often necessary to form a bend in the ultrasound catheter. Such bends are often crudely made in an operating room, vascular suite or other setting by a surgeon, cardiologist, interventional radiologist or other physician manually bending the catheter with pliers, surgical forceps or some other instrument. This technique has several drawbacks. First, it is inaccurate and does not always result in a bend at a desired location along the catheter or in a bend having a desired angle. Second, because the user bends the catheter when the catheter is already assembled, with the transmission member already in place, a strain is placed on the transmission member by the bending process. The transmission member is typically bent to as acute of an angle as the catheter body is bent, and the bending process itself stresses the transmission member. Even slight stresses placed on the transmission member by such a bending procedure may cause the transmission member to break prematurely, leading to a reduced usable life for the ultrasound catheter. This susceptibility for premature breakage is compounded by the fact that currently available ultrasonic transmission wires typically break toward their distal ends, where the cross-sectional areas of the wires become smaller.
Therefore, a need exists for ultrasound catheter devices and methods for making and using such devices that include at least one bend for enhancing positioning and/or advancement of the catheter in a blood vessel. Ideally, such catheter devices would be durable enough to last longer than a conventional ultrasound catheter that is hand-bent by a surgeon or other user immediately before use. Ultrasound catheters may also benefit from additional improvements, such as over-the-wire configurations, improved configurations of a distal head of the catheter, catheters that allow for various modes of operation, catheters with enhanced lubricity and the like. At least some of these objectives will be met by the present invention.